A current detection device based on tunneling magnetoresistance sensor and a measuring method

Abstract

The purpose of this invention is to provide a current detection device and measurement method based on a tunnel magnetoresistive sensor, belonging to the field of current sensor technology. The device features a base and a detachable wire fixing unit. Three tunnel magnetoresistive sensors are coaxially mounted on the base. The wire fixing unit supports adjustable range via a mechanical structure, while ensuring the wires are perpendicular to the sensor array plane, making the device more convenient and applicable to various complex application scenarios. Furthermore, the magnetic induction intensity at the locations of the three sensors is measured, the distance of the wires relative to each sensor is determined, and the current values ​​at the three test points are calculated and averaged to obtain the current value of the wires.

Description

Technical Field

[0001] This invention belongs to the field of current detection technology, specifically relating to a current detection device and measurement method based on a tunnel magnetoresistive sensor. Background Technology

[0002] With the emergence of the concept of smart grids, the integration of modern smart technologies with traditional technologies has driven the construction of a new generation of power systems. Accurate understanding of power network conditions can effectively reduce the costs associated with power outages, operational losses, and production efficiency losses. The need for accurate current measurement is pervasive in power grid systems. Whether measuring stable current during normal operation or transient current during system faults, high-quality current measurement methods are essential to achieving various control and metering objectives. Due to the limited space and dense wiring within distribution boxes, current sensors must meet requirements such as small size, simultaneous AC and DC measurement capability, low power consumption, and fast response.

[0003] Tunnel magnetoresistive (TMR) sensors are widely used in current detection in modern industry. Compared with traditional current transformers, they abandon the traditional bulky magnetic core structure and have advantages such as high sensitivity, large bandwidth, and low cost. They can also measure AC and DC currents simultaneously. Moreover, combined with printed circuit board technology, the relative positions between each sensor chip can be accurately located. Currently, the main coreless tunnel magnetoresistive current sensors mainly adopt a circular array structure (Yu Hao, Chang Wenzhi, Du Fei, et al. Research on anti-interference principle of current sensor based on circular array TMR [J]. Electric Power Information and Communication Technology, 2020, 18(10):7-14.DOI:10.16543 / j.2095-641x.electric.power.ict.2020.10.002). However, when installed in some narrow spaces, the circuit still needs to be disconnected, and it is difficult to ensure that the array plane is strictly perpendicular to the wire. This will cause the distance between each sensor to deviate from the set value, thereby introducing measurement error and making it difficult to guarantee measurement accuracy.

[0004] Therefore, how to design a current detection device based on a tunnel magnetoresistive sensor so that current detection can be carried out accurately and easily has become an urgent problem to be solved. Summary of the Invention

[0005] To address the problems existing in the background technology, the present invention aims to provide a current detection device and measurement method based on a tunnel magnetoresistive sensor. The device features a base and a detachable wire fixing unit. Three tunnel magnetoresistive sensors are coaxially mounted on the base. The wire fixing unit supports adjustable range through a mechanical structure, while ensuring the wires are perpendicular to the sensor array plane, making the device more convenient and applicable to various complex application scenarios. Furthermore, the magnetic induction intensity at the locations of the three sensors is measured separately, the distance of the wires relative to each sensor is determined, and the current values ​​at the three test points are calculated and averaged to obtain the current value of the wires.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A current detection device based on a tunnel magnetoresistive sensor includes a base and a detachable wire fixing unit.

[0008] Three tunnel magnetoresistive sensors are equally spaced on the same axis inside the base, and the sensitive axis of the tunnel magnetoresistive sensor is perpendicular to the axis.

[0009] The detachable wire fixing unit includes a telescopic rod base, an adjustable-length telescopic support rod, a nested ring base, an adjustable-diameter ring, and a ring diameter adjustment buckle. The telescopic rod base is fixedly connected to the base surface. One end of the adjustable-length telescopic support rod is fixedly mounted on the telescopic rod base, and the other end is fixedly connected to the nested ring base. The adjustable-diameter ring is vertically mounted on the nested ring base surface. The ring diameter adjustment buckle and the adjustable-diameter ring together are used to fix and place the current wire. The current wire always remains parallel to the plane of the base, i.e., perpendicular to the axis of the sensor center.

[0010] Furthermore, by adjusting the length of the adjustable telescopic support rod, the tunnel magnetoresistive sensor can always operate in the linear region, thus handling current measurement scenarios with different ranges.

[0011] Furthermore, the adjustable telescopic support rod is equipped with scales, which makes it easy to adjust the length directly to meet different current measurement scenarios.

[0012] Furthermore, the output terminal of the tunnel magnetoresistive sensor is connected to a signal processing circuit, which is used to calculate and process the magnetic induction intensity detected by the tunnel magnetoresistive sensor to obtain the current value in the current conductor.

[0013] Furthermore, the signal processing circuit includes an analog signal conditioning circuit, an ADC analog-to-digital converter, and an FPGA digital signal processing circuit. The analog signal conditioning circuit amplifies the differential voltage signal output by the tunnel magnetoresistive sensor and outputs the amplified signal to the ADC. The ADC samples the amplified analog signal and converts it into a digital signal for the FPGA to calculate the current value. The FPGA digital signal processing circuit drives the ADC to sample and calculate the current value sampled by the tunnel magnetoresistive sensor.

[0014] A measurement method for a current detection device based on a tunnel magnetoresistive sensor includes the following steps:

[0015] Step 1: Three tunnel magnetoresistive sensors measure the magnetic induction intensity B at their respective locations. i ,

[0016] i is the i-th tunnel magnetoresistive sensor, i = 1, 2, 3;

[0017] Step 2: Based on the magnetic induction intensity measured in Step 1, calculate the ratios k1 and k2 of the distances between each tunnel magnetoresistive sensor and the conductor to be measured.

[0018]

[0019] Where, r i This represents the distance from the tunnel magnetoresistive sensor to the center of the conductor under test, where 1, 2, and 3 represent sensor numbers 1, 2, and 3, respectively.

[0020] Step 3: Calculate the distances r1, r2, and r3 between the three tunnel magnetoresistive sensors and the conductor under test using the geometric relationship between them. The specific calculation formula is as follows:

[0021]

[0022]

[0023] Where θ is the angle between the line connecting the first sensor to the center of the conductor under test and the axis of the tunnel magnetoresistive sensor array, and d is the distance between two adjacent tunnel magnetoresistive sensors.

[0024] Step 4: Based on distance r i The current values ​​of the three tunnel magnetoresistive sensors are obtained by solving the Biot-Savart law, and the average value of the three current values ​​is then taken to obtain the current value I of the conductor under test.

[0025]

[0026] Where μ0 is the magnetic permeability in vacuum.

[0027] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0028] 1. The current detection device of this invention uses three tunnel magnetoresistive current sensors evenly spaced along a straight line. The entire device uses only three tunnel magnetoresistive sensors, while traditional circular array sensors require at least four sensors to reduce the error to 2%, which is necessary to improve anti-interference capability. In comparison, this device uses fewer sensors, reducing manufacturing costs and sensor power consumption. Moreover, in confined and complex measurement environments, it is difficult to ensure that the conductor under test is in the center of the array when installing circular array current sensors, and the original circuit needs to be disconnected. The linear array of the tunnel magnetoresistive array current sensor of this invention, combined with the conductor fixing unit, successfully solves this installation problem. By calculating the accurate distance from the sensor to the conductor, the measurement accuracy is effectively improved. With the distance known, the current measurement error of a single tunnel magnetoresistive sensor can be reduced to 0.5%.

[0029] 2. This invention uses a wire fixing unit to fix the wire to be tested, ensuring that the wire to be tested is always perpendicular to the sensor array plane, which greatly reduces the measurement error caused by installation. At the same time, the detection device provides a length-adjustable telescopic rod with scale and a diameter-adjustable ring, which enables the tunnel magnetoresistive array current sensor to be applied to current measurement scenarios of various ranges.

[0030] 3. This invention employs a coreless tunnel magnetoresistive current sensor for detection, overcoming the problem of residual magnetism in a magnetically saturated iron core. The detection device boasts high sensitivity, wide bandwidth, and small size, making it promising for broad applications in current measurement. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the current detection device based on a tunnel magnetoresistive sensor according to the present invention.

[0032] Figure 2 This is a schematic diagram of the adjustable diameter ring and the nested ring base of the present invention.

[0033] Figure 3 This is a schematic diagram of the measurement method of the current detection device based on the tunnel magnetoresistive sensor of the present invention.

[0034] Figure 4 This is a signal conditioning circuit diagram of the TMR2103 sensor chip in an embodiment of the present invention.

[0035] Figure 5 This is a block diagram of the tunnel magnetoresistive current sensor signal processing system in an embodiment of the present invention.

[0036] Figure 6 This is a circuit diagram of the power supply module used in an embodiment of the present invention.

[0037] Reference numerals in the attached figures: 1 is the first tunnel magnetoresistive current sensor, 2 is the second tunnel magnetoresistive current sensor, 3 is the third tunnel magnetoresistive current sensor, 4 is the base, 5 is the telescopic rod base, 6 is the length-adjustable telescopic rod, 7 is the nested ring base, 8 is the diameter-adjustable ring, and 9 is the ring diameter adjustment buckle. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0039] A current detection device based on a tunnel magnetoresistive sensor is shown in the schematic diagram below. Figure 1 As shown, it includes a base 4 and a detachable wire fixing unit;

[0040] Three tunnel magnetoresistive sensors (1, 2, 3) are equally spaced on the same axis within the base 4, and the sensitive axis of the tunnel magnetoresistive sensor is perpendicular to the axis.

[0041] The detachable wire fixing unit includes a telescopic rod base 5, a length-adjustable telescopic support rod 6, a nested ring base 7, a diameter-adjustable ring 8, and a ring diameter-adjusting buckle 9; wherein, the structural schematic diagram of the nested ring base 7 and the diameter-adjustable ring 8 is shown below. Figure 2 As shown, the telescopic rod base 5 is fixedly connected to the surface of the base 4. One end of the length-adjustable telescopic support rod 6 is fixedly mounted on the telescopic rod base 5 by screws, and the other end is fixedly connected to the ring nested base 7 by screws. The diameter-adjustable ring 8 is vertically mounted on the surface of the ring nested base 7. The ring diameter adjustment buckle 9 and the diameter-adjustable ring 8 work together to fix the current conductor to be measured. The current conductor to be measured is always perpendicular to the plane of the base 4.

[0042] When installing the current test lead, open the diameter adjustable ring 8 by adjusting the ring diameter adjustment buckle 9, then place the current test lead in the diameter adjustable ring 8, and then adjust the ring diameter by adjusting the ring diameter adjustment buckle 9 to completely fix the current test lead.

[0043] In high-current measurement scenarios, the length of the telescopic support rod can be adjusted by scale to increase the distance between the sensor and the wire, thereby ensuring that the magnetoresistive sensor always operates in the linear region. In low-current measurement scenarios, the length of the telescopic support rod can be shortened by scale to reduce the distance between the sensor and the wire and improve measurement accuracy.

[0044] Figure 3This is a schematic diagram illustrating the measurement method of the current detection device based on a tunnel magnetoresistive sensor according to the present invention. When the three tunnel magnetoresistive sensors are located on the same straight line, their distances from the conductor to be measured are r1, r2, and r3, respectively. The angle between the line connecting the first sensor to the center of the conductor to be measured and the axis of the tunnel magnetoresistive sensor array is θ. The conductor to be measured is always perpendicular to the plane of the sensor array, so the conductor to be measured can be regarded as a point and therefore can be equivalently represented as the triangle shown in the figure. The measurement method of the current detection device based on the present invention specifically includes the following steps:

[0045] Step 1: Three tunnel magnetoresistive sensors measure the magnetic induction intensity B at their respective locations. i ,

[0046] i is the i-th tunnel magnetoresistive sensor, i = 1, 2, 3;

[0047] Step 2: Based on the magnetic induction intensity measured in Step 1, calculate the ratios k1 and k2 of the distances between each tunnel magnetoresistive sensor and the conductor to be measured.

[0048]

[0049] Where, r i This represents the distance from the tunnel magnetoresistive sensor to the center of the conductor under test, where 1, 2, and 3 represent sensor numbers 1, 2, and 3, respectively.

[0050] Step 3: Calculate the distances r1, r2, and r3 between the three tunnel magnetoresistive sensors and the conductor under test using the geometric relationship between them. The specific calculation formula is as follows:

[0051]

[0052]

[0053] Where θ is the angle between the line connecting the first sensor to the center of the conductor under test and the axis of the tunnel magnetoresistive sensor array, and d is the distance between two adjacent tunnel magnetoresistive sensors.

[0054] Step 4: Based on distance r i The current values ​​of the three tunnel magnetoresistive sensors are obtained by solving the Biot-Savart law, and the average value of the three current values ​​is then taken to obtain the current value I of the conductor under test.

[0055]

[0056] Where μ0 is the magnetic permeability in vacuum.

[0057] Example 1

[0058] The tunnel magnetoresistive sensor uses the TMR2103 single-axis tunnel magnetoresistive sensor from Multidimensional Technology, which can achieve magnetic field sensing with an extremely wide dynamic range. The three tunnel magnetoresistive sensors are accurately positioned on the same straight line on the PCB base using Altuim Designer software, with the sensor sensitive axis perpendicular to the straight line where the three sensors are located. The distance between two adjacent tunnel magnetoresistive sensors is set to d.

[0059] Three uniaxial tunnel magnetoresistive elements (TMR2103), labeled S1-S3, are used to detect the magnetic field generated at that point on the conductor under test and output a differential voltage. Pin 3 of the TMR2103 chip is grounded, pins 4 and 5 are connected to pins 1 and 4 of the AD8221 respectively, pin 6 is connected to a 2.5V power supply, and pins 1, 2, 7, and 8 are left floating.

[0060] The output terminal of the tunnel magnetoresistive sensor is connected to a signal processing circuit. The signal processing circuit is used to calculate and process the magnetic induction intensity detected by the tunnel magnetoresistive sensor to obtain the current value in the current conductor. The signal processing circuit includes an analog signal conditioning circuit, an ADC analog-to-digital converter, and an FPGA digital signal processing circuit.

[0061] The circuit diagram of the analog signal conditioning circuit is as follows: Figure 4 As shown, this circuit amplifies the differential voltage signal output from the tunnel magnetoresistive sensor and outputs the amplified signal to the ADC analog-to-digital converter. The analog signal conditioning circuit includes three instrumentation amplifiers, specifically the Analog Devices AD8221, which is based on a three-op-amp topology. One preamplifier provides differential amplification to the voltage signal output from the sensor, while another differential amplifier eliminates common-mode voltage, converts the differential signal to a single-ended signal, and provides additional amplification. This amplifies the several millivolt differential voltage signal acquired by the sensor to several hundred millivolts, facilitating subsequent sampling and conversion into a digital signal by the ADC.

[0062] Pin 8 of the AD8221 is connected to the +5V power supply output of the ADP3336, pin 7 is connected to the low-pass filter circuit composed of resistor R4 and capacitor C3, pin 6 is connected to the +2.5V power supply output of the ADP3336, and a resistor with a resistance of 2.61KΩ is connected between pins 2 and 3. At this time, the amplification factor of the AD8221 is 20 times.

[0063] The signal processing block diagram of the overall system of the tunnel magnetoresistive current sensor device of the present invention is as follows: Figure 5As shown, the device employs a four-channel, 24-bit high-precision synchronous acquisition chip, AD4134, to synchronously acquire three amplified magnetic field voltage signals. The outputs of three AD8221s are connected to the analog inputs of the AD4134, while its digital outputs and control signals are connected to the FPGA module via SPI serial communication. The FPGA drives the ADC to perform high-speed synchronous sampling of the three channels, calculates the current value from the sampled signals, and uploads the calculated real-time current value of the conductor under test to the host computer via a USB interface.

[0064] The FPGA digital signal processing circuit uses the Cyclone II FPGA, which has powerful parallel processing capabilities.

[0065] The power supply module of the tunnel magnetoresistive current sensor device of the present invention is as follows: Figure 6 The +5V power input is connected to pins 6, 7, and 8 of the two ADP3336 chips. By adjusting the resistance ratio of R1 and R2, the output of the ADP3336 can be programmed to obtain a stable +5V voltage to power the AD8221 instrumentation amplifier and the FPGA. Similarly, adjusting the resistance ratio of R3 and R4 yields a stable 2.5V voltage, used to power the sensor chip and as a reference voltage for the instrumentation amplifier. Both the output and input voltages are grounded through a 1μF capacitor to filter out ripple and improve the overall stability of the tunnel magnetoresistive current sensor circuit.

[0066] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A current detection device based on a tunnel magnetoresistive sensor, characterized in that, Includes a base and a detachable wire fixing unit; Three tunnel magnetoresistive sensors are equally spaced on the same axis inside the base, and the sensitive axis of the tunnel magnetoresistive sensor is perpendicular to the axis. The detachable wire fixing unit includes a telescopic rod base, an adjustable-length telescopic support rod, a nested ring base, an adjustable-diameter ring, and a ring diameter adjustment buckle. The telescopic rod base is fixedly connected to the base surface. One end of the adjustable-length telescopic support rod is fixedly mounted on the telescopic rod base, and the other end is fixedly connected to the nested ring base. The adjustable-diameter ring is vertically mounted on the nested ring base surface. The ring diameter adjustment buckle and the adjustable-diameter ring together are used to fix and place the current wire. The current wire always remains parallel to the plane of the base, i.e., perpendicular to the axis of the sensor center.

2. The current detection device based on a tunnel magnetoresistive sensor as described in claim 1, characterized in that, The length of the adjustable telescopic support rod can be adjusted to ensure that the tunnel magnetoresistive sensor always operates in the linear region, which can be used to cope with current measurement scenarios with different ranges.

3. The current detection device based on a tunnel magnetoresistive sensor as described in claim 2, characterized in that, The adjustable telescopic support rod has graduations, which makes it easy to adjust the length directly when dealing with current measurement scenarios of different ranges.

4. The current detection device based on a tunnel magnetoresistive sensor as described in claim 1, characterized in that, The output terminal of the tunnel magnetoresistive sensor is connected to a signal processing circuit, which is used to calculate and process the magnetic induction intensity detected by the tunnel magnetoresistive sensor to obtain the current value in the current conductor.

5. The current detection device based on a tunnel magnetoresistive sensor as described in claim 4, characterized in that, The signal processing circuit includes an analog signal conditioning circuit, an ADC (Analog-to-Digital Converter), and an FPGA (FPGA Digital Signal Processing Circuit). The analog signal conditioning circuit amplifies the differential voltage signal output by the tunnel magnetoresistive sensor and outputs the amplified signal to the ADC. The ADC samples the amplified analog signal and converts it into a digital signal for the FPGA to calculate the current value. The FPGA drives the ADC to sample and calculate the current value sampled by the tunnel magnetoresistive sensor.

6. A measurement method for a current detection device based on a tunnel magnetoresistive sensor, characterized in that, Includes the following steps: Step 1: Three tunnel magnetoresistive sensors measure the magnetic induction intensity B at their respective locations. i , i is the i-th tunnel magnetoresistive sensor, i = 1, 2, 3; Step 2: Based on the magnetic induction intensity measured in Step 1, calculate the ratios k1 and k2 of the distances between each tunnel magnetoresistive sensor and the conductor to be measured. Where, r i This represents the distance from the tunnel magnetoresistive sensor to the center of the conductor under test, where 1, 2, and 3 represent sensor numbers 1, 2, and 3, respectively. Step 3: Calculate the distances r1, r2, and r3 between the three tunnel magnetoresistive sensors and the conductor under test using the geometric relationship between them. The specific calculation formula is as follows: Where θ is the angle between the line connecting the first sensor to the center of the conductor under test and the axis of the tunnel magnetoresistive sensor array, and d is the distance between two adjacent tunnel magnetoresistive sensors. Step 4: Based on distance r i The current values ​​of the three tunnel magnetoresistive sensors are obtained by solving the Biot-Savart law, and the average value of the three current values ​​is then taken to obtain the current value I of the conductor under test. Where μ0 is the magnetic permeability in vacuum.

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